In the present study, we investigated taste-taste, taste-vehicle, and
simultaneous taste-vehicle-taste mixtures. Subjects made estimates of
the sweetness and bitterness of 27 stimuli. Sucrose (292, 585, and 117
0 mM), caffeine (13, 26, and 52 mM), and binary mixtures of low (292-1
3 mM), middle (585-26 mM), and high (1170-52 mM) levels of both compon
ents were dispersed in water, carboxymethylcellulose (CMC) 1% w/v, and
gelatin 6% w/v. The sweetness and bitterness of the sucrose-vehicle-c
affeine combinations were significantly weaker than the respective suc
rose-vehicle and caffeine-vehicle combinations. The emerged mutual sup
pressive effects were asymmetrical and persisted when both tastants we
re presented in CMC and gelatin. Moreover, the increase in vehicle con
sistency and the simultaneous addition of another taste reduced the pe
rceived intensity of a taste either presented alone or dissolved in wa
ter. For both sweetness and bitterness, the total taste suppression ob
served was always significant.